Generally, in the process of acquiring seismic data, recording instruments responsive to ground motion are selectively positioned and coupled to the earth above the subterranean formation of interest. Seismic energy generated and transmitted into the earth imparts motion to the area of the earth proximal to origin of the seismic energy. In some instances, recording instruments responsive to motion generate a signal, generally in the form of voltage, proportional to ground motion.
Collecting and processing these signals requires electrically connecting, via electrical conduits, the recording instruments to seismic processing equipment. From time to time, it is desirable to selectively connect and disconnect the recording instruments from the electrical conduits during seismic data acquisition. In these instances, plug connectors having environmental seals, referred to as "plug boots", secured to robustly insulated electrical conduits are used.
Polyurethane is a common elastomeric material used in manufacturing such plug boots and conduits. Generally, the polyurethane plug boot is formed continuously with a polyurethane-jacketed electrical cable. The extending end of the plug boot is generally provided with a continuous lip for oversealing engagement with a mating plug.
Under mild temperatures, the polyurethane lip provides an adequate environmental seal at the union of the two plugs. However, at extreme temperatures (at about -55.degree. C. and at about 80.degree. C.), the polyurethane boot may stiffen when exposed to frigid temperatures, or become overly pliable when exposed to warmer temperatures. Additionally, the coefficient of compression of polyurethane is such that after repetitive engagements, the polyurethane lip may cease to adequately overseal with the mating plug. "Memory loss" is a term commonly used to describe the failure of the polyurethane lip to provide such overseal after repetitive engagements.
Another elastomeric material used in the manufacture of plug boots and conduits is neoprene. Generally, neoprene boots provide an adequate environmental seal over a wider temperature range than thermoplastics, including polyurethane, and also exhibit superior "memory" after repetitive engagements. However, neoprene jacketed cables have been found to be less robust than polyurethane-jacketed cables. Thus there exist the need for an electrical conduit and a reliable method of making the same that combines the superior sealing ability of neoprene and the superior robust qualities polyurethane.